High frequency device



N. E. LINDENBLADi HIGH FR Aag. a, 1957 QUENCY DEVICE 2' Sheets-Sheet 1 Filed Jan. 25, '1941 O OQ All All AIAA VVVVVVV 'VVV -lllllllllllil- INVENTOR NILS E. LiNDENBLAD BY Aug. 6, 1957 N. E. LINDENBLAD HIGH FREQUENCY DEVICE 2 Sheets-Sheet 2 Filed Jan. 25. 1947 lllllgglllllh- ALONG HEL/X 6,'

INVENTDR NILS E. LINDENBLAD BY M ATTORNEY United States Patent O 2,802,136- rHIGH FREQUENCY DEviCn Nils E. Lindenblad, Port Jefferson, N. Y., assignor yto Radio Corporation of America, a corporation of Deia- Ware l Application January 2s, 1947, serial No. 724,330 32 Claims. (Cl. sis- 3.5)

i This invention relates to electron discharge devices and circuits therefor, especially adapted for use at very high frequencies, and particularly to an electron discharge device capable of operating on a band of frequencies such.

as would be required in a radio relay system.

An object of the linvention is to provide a novel type of electron discharge amplifier device and circuit therefor for use with `a Wide band of rvery highfrequenciesvand which does Vnot depend upon resonance phenomenon in the output circuit.

Other objects will appear from a reading of the following description, in conjunction with a drawing, wherein:

Figs. l, 2 and 3 illustrate different embodiments of the electron discharge device of the invention; and A Fig. 3a is a graph showing the voltage distribution along the helix 6' of Fig. 3.

Referring to Fig. l in more detail, there lis shown a i wide band amplifier device comprising a non-magnetic metallic envelope 10 (for example, copper) dividedfinto two chambers 12 and 13 by means of a metallic partition 11. Partition 11 has an aperture 15 thereinlfor enabling the passage therethrough of an electron stream' or beam, shown by the dash line, emanating Ifrom a cathode K. The electrons-from the cathode K pass through tubular focussing and accelerating electrodes 16 and 17 arranged in a conventional vmanner known to those familiar with the cathode ray arti y I 4 Y Surrounding the electron stream in chamber 12 and closely coupled to the electron stream is anvinput conducting helix-S one endv of which is connected to the inner conductor of a coaxial input line 37, land the other end of which is -terminated by a resistor R whose value matches the impedance ofthe helix 5. Helix 5 is a plurality of wavelengths long peripherally along the helix at the center frequency of operation. Resistor RV prevents the reection of waves which travel along helix 5. It should be noted that the inner conductor-of input line 37 is spirally tapered in a direction to match the impedance of helix 5 to which it is connected. In this Way, the input line may change impedance from a valuefof the order of 50 ohms to an order of magnitude of several hundred ohms so as to match the impedance of that end of the helix 5 which is connected to line 37.

Helix 5 is arranged to surround and be'relatively close to the electron stream for close coupling to the stream. The closer the helix 5 is to the surrounding non-magnetic envelope 10, the lower will be its impedance and the easier it will be to match this impedance with the input line, due to the lower impedance transformation ratio required. If the helix is too close to the envelope 10, the coupling between the helix and the electron stream will be unduly reduced. Hence the ratio of the inside diameter of the metallic envelope 10 and the helix 5 is so chosen as to obtain the necessary coupling between helix 5 and electron stream. The diameter of helix Sis sufficiently large to permit the desired internal and axial electric held components which may react with the axially moving electron stream. This factor must be con- 2,832,136 Patented Aug. 5, 1957 sidered in the design of the electron discharge device and alfects the dimensions of the device. It will thus be `seen that chamber 12 may be considered as the input chamber.

Chamber 13, which can be considered the output chamber, comprises a non-magnetic metallic envelope 18 which is insulated by dielectric material 19 from the outer nonmagnetic envelope 10. Contained within the chamber is a tapered pitch helix 6 which surrounds and is closely coupled to the electron stream passing axially therein. One end of helix 6 is terminated by impedance matching resistor Rwhile the other end of the helix is connected to the inner conductor of the output coaxial line 20. Resistor R prevents the reilection of waves which travel along helix 6. The inner conductor of output line 20 is spirally tapered more closely at the end which connects with helix 6 than at the end which extends to the load, not shown. The tapering enables the output line 20 to match the impedance of the helix 6. The same principles mentioned4 above in connection with the tapering of the inner conductor of the input line apply equally to the tapering of the output line. Similarly, the same factors involving diameters of helixand surrounding envelope previously mentioned in relation to the coupling of input helix 5 to the electron stream apply equally to the coupling of the vhelix 6 to the electron stream. Helix 6 is also a pluralityof wavelengths long peripherally along the helix at the center frequency of operation.

A collector electrode 21 serves to collect the electrons which finally pass axially through the helix 6. This collector electrode is maintained at a positive potential relative'to the cathode by means of battery B. It should be noted that the battery B is connected to ground at its positive terminal and that this positive terminal is connected to metallic tube 18 of the output chamber through lead 22. The negative terminal of battery B is connected to the-cathode K via lead 23. The battery is bridged by a potentiometer P. Electrodes 18 and 17 are connected to spaced tapping points onpotentiometer P by means of leads 122 and 123, respectively. The outer metallic envelope 10 is also connected to a tapping point on potentiometer P by means of lead 24. The connections to potentiometer P and battery B are such that envelope 10 is at a relatively positive potential with respect to the cathode K, electrode 17 at a relatively less positive potential relative to cathode K, electrode 16 at a still less positive potential relative to cathode K, while metallic tube 18 of the output chamber is at a very high positive potential relative to the cathode K. It will thus be seen that there is a potential difference between metallic envelope 10 of chamber 12 and metallic tube 18 of chamber 13. The collector 21 is shown directly connected to the positive terminal by means of lead 124 and lead 22. The dotted lines 25 indicate that, if desired, a battery may be inserted to maintain the collector electrode 21 at a slightly positive potential relative to the metallic tube 18.

A magnetic iield coil 26 surrounds -the nonmagnetic envelope 10 for producing an axial magnetic eld for controlling the electron beam. This coil 26 is yshown energized by a battery 27 through an adjustable resistor 28. In effect, the magnetic eld produced Iby coil 26 acts to focus the electrons along the longitudinal axis of the device and to prevent dispersion of the stream along its path of travel. This magnetic field should be so distributed as to produce the desired focussing action throughout the length of the device in view of varying electron velocity conditions discussed later. It will -be evident that other means for producing a focussing action may be used instead of the coil 26.

`,In the `operation of the system, very high frequency waves, for example microwaves, are applied to the input line 37 and, in turn, applied to helix 5. Helix 5 has a ratio between its diameter and pitch such that a travelling wave thereon produced by the incoming signal has an axial velocity slightly greater than the electron velocity in chamber 12 in order to deliver power to the electron stream for vhunching the electrons in the stream. The pitch of the helix may or may not be tapered to achieveA this effect.

The electrons are hunched in chamber 12 `and pass through aperture 15 in metallic partition 11. This partition acts as a shield against electromagnetic coupling between input chamber 12 and output chamber 1'3; in other words, prevents feedback between the waves travelling on the two helices 5 and 6.

' Helix 6 has a travelling wave producedthereon by the electrons which enter chamber 13 after being hunched in chamber 12. A high order of amplification is obtained in chamber 13. The hunched electrons immediately entering chamber 13 are accelerated due to the factlthat a potential difference exists between the metallic envelope of chamber 12 and the metallic tube 18 of chamber 13. Chamber 12, is in effect, at a negative potential relative to chamber 13. The electrons entering chamber V-13 andaccelerated by this potential difference enter the interior of helix 6 and induce a travelling wave on helix 6 whose axial velocity is somewhat less than the velocity of the electron stream which passes through helix 6. The electron stream in chamber 13 delivers power to vhelix 6 and lis therefore decelerated in this process. .In order to continually extract energy from the electron stream alongttheentire length of the helix 6 and to reduce the velocity of the electron stream as much as possible before the electrons are gathered up by collector Zl, it is advantageous to taperthe pitch of helix 6, as shown, so that this taper corresponds with the deceleration of the electron stream. This taper in pitch of helix 6 is necessary'in order to maintain the desired relation, described above, in which the wave velocity is somewhat less than the velocity of the electron stream, throughout the length of helix 6. It is important` to note that the electron stream entering chamber 13 from aperture 1S is accelerated only until it reaches the first turn of the hollow helix 6, after which there is no further acceleration of the stream within the helix 6 because there is no D. C. field established within helix 6 itself. i

In chamber 12, likewise, the electrons are originally accelerated before they reach the input helix 5. Once the electrons enter the helix 5 they are no longer influenced by any D. C. 4accelerating electric field but are affected by the radio frequency field produced Vby the signal wave travelling along the input helix 5 which then causes `hunching of the electrons. The Vkinetic energy given to the electrons by the D. C. field before entering the input helix 5 and from the radio frequency field, from the signal wave, during passage of the electrons through the helix 5 also serves to eject the electrons through the aperture into the chamber 13. The hunching action is caused hy the electricfield distribution of the signal wave causing transient velocity variations in the electrons in the stream, resulting in grouping. In chamber 13 the hunched electrons come under the influence of a D. C. field before entering ,the output helix 6 and are Vgiven very `considerable additional acceleration. After having entered helix 6, the hunched accelerated electrons will have their hunching accentuated and will also begin to deliver power to the helix 6 and become decelerated.

`It should be noted at this time that both conductors of the output line are grounded, whereasV both conductors of input line 37 are at a negative potential. It is therefore necessary to provide an isolating junction (condenser, for example) between the input line 37 and the apparatus which feeds` the line 37 with incoming signals.

Fig. 2 is a modification of Fig. 1 and shows a system like that of Fig. 1 except that the outer non-magnetic envelope 10 is grounded, thus permitting grounding of the outer conductor of the input line 37. The same parts in Figs. l and 2 have been designated bythe same reference,

characters. The conductors of the output line 20 of Fig. 2 are at a positive potential relative to the cathode and to ground. The operation of the electron discharge device of Fig. 2 is the same as that of Fig. 1.

Fig. 3 shows another embodiment of the invention. Those parts of this ligure which are identical with those of Figs. 1 and 2 have been given the same reference characters. In Fig. 3, the output helix is designated 6 and is composed of separate sections having overlapping ends 50, 51 which are capacitatively `coupled together to form a continuous path for the energy of the traveling wave along the helix, but the junction of which introduces a resistance voltage drop for direct current. In efect the sections are coupled together by a substance 67 interposed between said overlapping ends lwhich is chiefly dielectric for radio frequencies and is a resistance for direct current. Hence, the sections are capacitatively coupled together for the travelling wave. Various types of semiconductors such as titanium dioxide may serve for this purpose. The right hand end of output helix 6' is connected to the positive terminal of battery B' via lines 30 and 31. The left hand end of helix 6' is connected through resistor R to the metallic tube 18 of chamber 13, as in Figs. l and 2. Tube 18 is connected hy line 32 to an intermediate point on battery B' so that the helix 6 is given an axial potential gradient to thereby cause augmentation of the acceleration of the hunched electrons while travelling through the helix''.

Conductor 30 passes through the quarter wave sleeve 60' located in the metallic enclosure 61. This conductor is coupled to the enclosure 61 for radio frequency energy bythe blocking condenser 62. The conductor 30 is however, insulated from enclosure 61 by the blocking condenser 62 `for direct current and is connected to D. C. lead 31 so that the helix 6 can be energized with direct current.

Fig. 3a shows the voltage distribution along the output helix 6. This voltage distribution increases in value asthe distance of the helix from the metallic shield partition 11 increases.

What is claimed is:

l. An electron discharge device comprising first and second hollow chambers placed end-to-end, means including a source of electrons for projecting a focussed stream of electrons along apath from said first chamber into said second chamber, said chambers being electrically insulated from each other, a helical conductor in each of said chambers surrounding a portion of the path of said stream and coupled to the electron stream, the adjacent ends of said helical conductors being spaced apart for preventing propagation of waves from one conductor to the other, a signal input line coupled to the helical conductor in said first chamber forproducing a traveling wave thereon for separating the electrons into hunched groups, an output line coupledto the helical conductor in said second chamber, said groups of electrons entering said second chamber functioning to induce a traveling wave on thethelcal conductor in said second chamber.

2. An electron discharge device comprising first and second hollow chambers placed longitudinally `end-tc-end, means including a source of electrons in said first chamber and an element in said second chamber adapted to b e maintained at a positive potential relative to said source for projecting a focussed stream of electrons along a path from said first chamber into said second chamber, aconducting helix in each of said chambers surrounding said path and coupled to the electron stream in energy transfer relation, the adjacent ends of said helical condvuctors being spaced apart for preventing propagation of waves from one conductor to the other, means coupled to the helix in said first chamber for producing a traveling 'wave thereon with an axial velocity greater than the velocity of the electrons in Asaidchamber, whereby power is delivered to said electrons for hunching them into groups, a termination for the helix in said second chamber,

and means for accelerating the bunched electron stream prior to its entry into the helix in said second chamber to a velocity greater than the axial velocity of the traveling wave induced on said last helix by the electron stream.

3. An electron discharge device comprising first and second chambers placed end-to-end in a longitudinal direction, a .shield separating said chambers and having an aperture therein, means including a source of electrons and a focussing system adapted to affect the electrons emanating from said source for passing a focussed stream of electrons from said first chamber along a path through said aperture into said second chamber, a conducting helix a plurality of wavelengths long at the operating frequency peripherally along the helix in each of said chambers adjacentsaid path, each of helices being in energy transfer relation to said electron stream, the adjacent ends of said helices being spaced apart for preventing propagation of waves from one helix to the other, a signal input transmissionline coupled to that end of the helix in said first chamber which is farthest removed from the second chamber for applying very high frequency waves to said helix, means coupled to and terminating the other end of the helix in said first chamber and having an impedance which substantially matches the impedance of said helix, means coupled to and terminating that end of the helix in said second chamber which is nearest the first chamber and having an impedance which lsubstantially matches-the impedance of the helix in said second chamber, the helix in said second chamber having a changing pitch such that the turns of this last helix come closer together as the distance increases from said shield, and an output transmission line coupled to .the helix in said second chamber.

4; An electron discharge device comprising rst and second hollow chambers placed end-to-end, means including a source of electrons and a focussing system adapted to affect the electrons emanating from said source for passing a focussed stream of electrons along a path from said first chamber into lsaid second chamber, a conducting helix vin each of said chambers a plurality of wavelengths long at the operating frequency peripherally along the helix positioned adjacent said path, said helices being in energy transfer relation to the electron stream, the adjacent ends of said helices being spaced apart for preventing propagation of waves from one helix to the other, means coupled to and terminating said helices in substantially refieotionless manner for waves traveling along the turns of the helices, the helix in said second chamber having a changing pitch, a signal input transmission line coupled tothe helix in said first chamber, and an output transmission line coupled to the helix in said second chamber.

5. An electron discharge device comprising first and second hollow chambers made of non-magnetic metal and placed end-to-end, means for passing a focussed stream of electrons from said first chamber into said second chamber through an aperture, an apertured partition substantially shielding said chambers from each other, said means including a source of electrons in said first chamber at a distance removed from said second chamber and a focussing system adapted to affect the electrons emanating from said source, a conducting helix in each of said chambers a plurality of wavelengths long at the operating frequency peripherally along the helix, said helices being in energy transfer relation to ythe electron stream, the adjacent ends of said helices being spaced apart for preventing propagation of waves from one helix to the other, means coupled to and terminating said helices in substantially reflectionless manner for waves traveling along the turns of the helices, the helix in said second chamber having a changing pitch, a signal input transmission line coupled to the helix in said first chamber, an electron collector electrode in said second chamber, and an output transmission line coupled to the helix in said second chamber.

Vv6. A11 electron discharge device comprising first and second chambers placed end-to-end, means including a source of electrons and a focussing system adapted to affect the electrons emanating from said source for passing a focussed stream of electrons along a path from said first chamber into said second chamber, a conducting helix in each of said chambers a plurality of wavelengths long at the operating frequency peripherally along the helix, positioned adjacent said path, said helices being in energy transfer relation to the electron stream, the adjacent ends of said helices being spaced apart for preventing propagation of waves from one helix to the other, a signal input transmission line coupled Ito that end of the helix in said first chamber which is located farthest away from said second chamber, a resistor connected to the other end of the helix in said first chamber and having a value which substantially matches the impedance of said last helix, a resistor connected to that end of the helix in said second chamber which is nearest said first chamber and having a value which substantially matches the irnpedance of the helix in said second chamber, an output transmission line coupled to the other end of the helix in said second chamber, said helix in said second chamber having a changing pitch along its axial length, and an electron collector electrode for gathering the electrons which pass beyond the helix of said second chamber.

7. An electron discharge device in accordance with claim 6, wherein said signal input transmission line and said output transmission line are matched with the impedances of the helices to which they are respectively coupled.

8. In an electron discharge device, means in said device near one end thereof for producing a stream of charged particles along a path, a helical conductor a plurality of wavelengths long at the operating frequency peripherally along the turns thereof adjacent said path and in energyV transfer relation to said stream for modulating the same, means coupled to said helical conductor for applying modulating waves thereto, and another helical :conductor located further along the path of said stream and adjacent said path and in energy transfer relation to the modulated stream for extracting energy from the stream, said last helical conductor being spaced from said first helical conductor and having a changing pitch and also being a plurality of wavelengths long peripherally along the turns thereof at the operating frequency.

9. In an electron discharge device, means in said device near one end thereof for producing a stream of charged particles along a path, a helical conductor `a plurality of wavelengths long at the operating frequency peripherally along the turns thereof adjacent said path and in energy transfer relationto said stream for modulating the same, means coupled to said helical conductor for applying modulating waves thereto, means for accelerating the modulated electron stream, and another helical conductor located farther along the path o-f said stream and also adjacent said path 'and in energy transfer relation to the modulatedaccelerated stream for extracting energy from the stream, said last helical conductor being spaced from said first helical conductor and having a changing pitch and also being a plurality of wavelengths long peripherally along the turns thereof at the operating frequency.

l0. An electron discharge device comprising a pair of hollow chambers separated by a shield having an aperture therein for the passage of electrons therethrough, said chambers being electrically insulated from each other, a cathode in one chamber and a collector electrode in the other chamber, means along the path of the electrons which emanate from said cathode for focussing the electrons into a stream whose path passes through said aperture, a helix in said one chamber adjacent said path and in energy coupling relation to said stream for modulating said electrons, and a helix in the other chamber also adjacent said path and in energy coupling relation to the electron stream therein for extracting power from said modulated stream, the adjacent ends of said helices beingspaced apart for preventing propagationof 4Waves frornlone helix tothe other.

`1l. An electron discharge device comprising `lirst and second chambers separated by ashieldrhaving an aperture therein for the passage of electrons therethrough, a cathode in said rst chamber and a collector electrode in said second chambenmeans adjacent atleast one of said chambers for producing magneticilux lines ,parallel to said stream in the space between said cathode and said collector electrode for focussing the electrons which emanate from said cathode into a stream Whose path passesthrough said aperture, a helixin said first chamber located between said cathode and saidshield and adjacent said path and in lenergy transfer relation to `said stream, a coaxial inputline coupled toene end of said helix for supplying radio frequency signal waves thereto, the inner conductor of said input line being helical and tapered `in a direction to match the `impedance of the helix in said first chamber, a resistance terminating the otherzend of said helix, a helix in said second chamber located between said shield and the collector electrode and adjacent said path and in energy coupling relation to` said stream, a resistor terminating that end of said last helix .which is nearest said shield, and an output coaxial line coupled to the other end ofthe helix in said second chamber, the inner conductor of said output line being helical and tapered in a direction to match the impedance of thehelix in the second chamber, the helixes in both chambers each having a peripheral length which is a plurality of wavelengths long at the operating frequency.

l2. An electron discharge device comprising first and second chambers separated by a shield having an aperture therein for the Vpassage of electrons therethrough, a cathode in said rst chamber and a collector electrode in said second chamber, means adjacent said chambers for acting in the space between said cathode and collector elcctrede for focussing the electrons which emanate from said cathode 4into a stream whose path passes through said aperture including means for producing an axial magnetic field acting on said stream, a helix in said first chamber located between said cathode and said shield and adjacent said path and in energy transfer relation to said stream, a coaxial input line coupled to one end of said helix for supplying` radio frequency signal waves thereto, the inner conductor of said input line being helical and tapered in a direction to match the impedance of the helix in said first chamber, a resistance terminating the other end of said helix, a helix in said second chamber located between said shield and the collector electrode and adjacent said path and in energy coupling relation to said stream, a resistor terminating that end of said last helix which is nearest said shield, and an output coaxial line coupled to the other end of the helix in said second chamber, the inner conductor of said output line being helical and tapered in a direction to match the impedance of the helix in the second chamber, the helixes in both chambers each having a peripheral length which is a plurality of wavelengths long at the operating frequency, the helix in said second chamber having a changing pitch such that the turns of said last helixare closer as the distance from said shield increases.

13. An electron discharge device comprising a pair of hollow chambers separated by a shield having an aperture therein for the passage of electrons therethrough, a cathode in one chamber and a collector electrode in the other chamber, means adjacent said chambers for focussing the electrons which emanate from said cathode into a stream whose path passes through said aperture, a helix in said one chamber adjacent said path and in energy coupling relation to said stream for modulating said electrons, and a helix in the other chamber adjacent said path and in energy coupling relation to the electron stream therein for extracting power from said modulated stream, the adjacent `ends of `said helices being spaced' apart for preventing propagation of waves from one helix ,to the other, an input line having an .impedance matching the impedance of the helix in said one chamber and coupled thereto for supplying radio frequency waves thereto, an output line coupled to the helix in the other chamber, said last helix being tapered in pitch in a direction which brings the turns of the helix closer together as the output line is approached.

14. An electron discharge device comprising a pair of chambers separated by a shield having an aperture therein for the passage of electrons therethrough, a cathode in one chamber adapted to emit electrons and a collector electrode in the other chamber, means adjacent said chambers forfocussing the electrons which emanate from said cathode into a stream along a path passing through said aperture, a helix in said one chamber adjacent said path and in energy coupling relation to said stream for modulating said electrons, and a helix in the other charnber adjacent the path of said stream and in energy cou pling relation to the electron stream passing through said other chamber for extracting power from said modulated stream, an input line having an impedance matching the impedance of the helix in said one chamber coupled thereto for supplying radio frequency waves thereto, an output line coupled to the helix in the other chamber, said last helix being tapered in pitch in a direction which bringsthe turns of the helix closer together as the output line is approached, said last helix being sectionalized with the sections overlapping and separated by a substance which is chiefly dielectric for the alternating current energy traveling peripherally along said helix but introduces a resistance voltage drop for direct current, and means coupled to the output end of said last helix for supplying the same with a potential which is positive relative to said cathode.

15. An electron discharge device comprising an envelope, means within said envelope for projecting a stream of electrons along a path through the interior of said envelope, a helical conductor located adjacent said path in energy coupling relation to the stream, said helical conductor being a plurality of wavelengths long peripherally at the operating frequency, a coaxial line coupled to one end of said helical conductor, the inner conductor of said line being helical and tapered such that its turns are more closely spaced near said helical conductor than farther away therefrom so as to substantially match the impedance of said helical conductor.

16. An electron discharge device comprising an envelope, means within said envelope for projecting a stream of electrons along a path through the interior of said envelope, a helical conductor located adjacent said path and in energy coupling relation to the stream, said helical conductor being a plurality of wavelengths long peripherally at the operating frequency, a coaxial line coupled to one end of said helical conductor for supplying radio frequency waves thereto, a resistor terminating the other end of said helical conductor and having a value to substantially match the impedance of said helical conductor, the inner conductor of said coaxial line being helical and tapered such that its turns are more closely spaced near said helical conductor than farther away therefrom so as to substantially match the impedance of said helical conductor.

17. An electron discharge device comprising an envelope, means for projecting a stream of electrons through the interior of said envelope, a helical conductor adjacent said stream and in energy coupling relation thereto, said helical conductor being a plurality of wavelengths long peripherally at the operating frequency, said helical conductor being composed of a plurality of overlapping sections, a substance separating adjacent overlapping sections of said helical conductor, said substance having a. low impedance path for alternating currents passing over said helical conductor and having said characteristics that it introduces a resistance voltage drop for direct current flowing over said Ahelical conductor, and means vcoupled to said helical Vconductors for supplying direct current thereto, whereby there is an axial potential gradient along said conductor.

18. An electrondischarge device comprising an envelope, means for projecting a stream of electrons through the interior of said envelope, a helical conductor adjacent said stream and in energy coupling relation thereto, said helical conductor being a plurality of wavelengths long peripherally at the operating frequency, said helical conductor being composed of a plurality of overlapping sections, a substance separating adjacent overlapping sec tions of said helical conductor said substance being chiefly dielectric for radio frequency currents passing over said helical conductor, whereby adjacent overlapping sections are capacitively coupled together for radio frequency currents.

19. An electron discharge device amplifier comprising first and second chambers arranged end-to-end composed of non-magnetic metallic material, a shield separating said chambers and having an aperture therein through which electrons may pass, a cathode in said first charnber near one end, means for projecting an electron stream from said cathode along a path through said aperture into said second chamber, separate helical conductors in said chambers adjacent said path and in energy transfer relation to said stream, a radio frequency input circuit coupled to the helical conductor of said rst chamber, a radio frequency out-put circuit coupled to the helical conductor of said second chamber, resistors terminating said helical conductors at their ends nearest said shield, said helical conductors being each a plurality of wavelengths long peripherally at the operating frequency, the helical conductor in said second chamber being tapered in pitch such that its turns are more closely spaced at a distance removed from said shield than at the portion near the terminating resistor, and means coupled to said helical conductors for maintaining the helix in said second charnber at a positive potential relative to the helix in said first chamber, whereby the electrons entering said second chamber are accelerated before the stream enters the space adjacent the helix in said second chamber.

20. An amplifier in accordance with claim 19, including means for grounding the first chamber and for supplying a positive potential to said second chamber relative to said first chamber.

21. An amplifier in accordance with claim 19, including means coupled to said chambers for maintaining the rst chamber at a positive potential and said second chamber at a higher positive potential relative to said cathode.

22. A helical conductor composed of separate sections having overlapping ends, a substance interposed between said overlapping ends, said substance being chiefly dielectric for alternating currents which may pass over said conductor and providing a resistance voltage drop for any direct current which may pass over said helical conductor.

23. An electron discharge device comprising means for producing an electron stream along a path, a helical conductor adjacent said path and in energy transfer relation to electrons passing along said path, said helical conductor being composed of separate sections, having overlapping ends, and titanium dioxide separating said overlapping ends.

24. An electron discharge device in accordance with claim 18, including means coupled to a point on said helical conductor appreciably removed from the source of the electrons for supplying a direct current potential thereto.

25. An electron discharge device comprising a pair of hollow chambers insulated from each other separated by a shield having an aperture therein for the passage of electrons therethrough, means including Va cathode iii one chamber for projecting a stream of electrons along a path extending through said aperture, a helix in said one chamber adjacent said path and in energy coupling relation to said stream for modulating said electrons, and a helix in the other chamber also adjacent said path and in energy coupling lrelation to 'the' electron stream therein for extracting power from' said vmodulated stream, the adjacent ends of said helices being spaced apart for preventing propagation of waves from one helix to the other.

26. An electron discharge device comprising a conducting chamber, means for projecting a stream of electrons along a path within said chamber, a helical conductor located adjacent said path -and in energy coupling relation to the stream, said helical conductor being a plurality of wavelengths long peripherally at the operating frequency, a coaxial line having its outer conductor coupled to said chamber and its inner conductor coupled to one end of said helical conductor, a resistor connected between the other end `of said helical conductor and said chamber and having a value to substantially match the impedance of said helical conductor, said inner conductor of said coaxial line being helical and tapered in pitch such that its turns are more closely spaced near said helical conductor than farther away therefrom so as to substantially match the impedance of said helical conductor.

27. A device in accordance with claim l comprising means including a source of direct current Voltage connected to said helical conductors for accelerating said stream between said conductors.

28. An electron dischargev device comprising two axially-aligned, spaced helical conductors constituting input and output coils, two shields separately enclosing said two coils, resistive means connected between each of the adjacent ends of said coils and the respective enclosing shield for preventing reflection of waves traveling along said coils, insulating means separating said shields to permit application of different direct current potentials to said coils, means coupled to the opposite end of said input coil for applying signal energy thereto, means coupled to the opposite end of said output coil for deriving energy therefrom, and means adjacent said opposite end of said input coil for producing a stream of electrons along a path extending along said coils.

29. An electronic amplifier device comprising an envelope containing means for projecting an electron beam along a path, and plural sections of conductive 4helix in succession along said electron beam path, said sections being insulated apart entirely for direct-currents within said envelope and having separate external terminals.

30. An electronic amplifier device including means for projecting an electron beam along a path, input modulating means closely adjacent to that path for imparting input signal modulation to the beam, output-signal deriving means at the opposite end of that path, plural sections of conductive helix located in succession along the electron beam path, said sections of helix being separated by electrical insulation, and separate terminals for energizing said sections at different beam-accelerating directcurrent potentials.

31. An electronic amplifier including means for projecting an electron beam along a path, means for guiding the propagation of electromagnetic waves along said path whereby said beam is modulated in accordance with the propagated waves, said guiding means having a dilerent relationship to the beam projecting means at the input end thereof than at the output end, these relationships affording a wave velocity slightly greater than the beam velocity at the input end and a wave velocity less than the beam velocity at the output end of the beam path.

32. An electronic amplifier according to claim 31, wherein said guiding means is divided into plural sections mutually `insulated `apart `and having 4separate external,

terminals.

"lil

References Cited in the le `of -thispatent UNITED STATES PATENTS 12 Clavier et al. July 14, ,1942 Lindenblad Oct. 27, 1942 Cassen Dec. 8, 1942 Llewellyn Ian. 16, 1945 Knol et a1. Nov. 4, 1952 Pierce Apr. 28, 1953 

